Radar Cheat Sheet- 1st Exam

Eng-Sa’di Y. Tamimi October 15, 2013
These notes can be used as helping material to prepare you to the ﬁrst exam. So refer to it while you are studying, to test your understanding. Note that these notes cover most of the material’s parts (but do not include everything), so it cannot be used as an alternative to the text-book. The Radar systems material is divided into three parts as shown below:

1

Basic Concepts

This part is descriptive by its nature! In this part, you are required to deﬁne, describe, and talk about the basic Radar concepts such as: 1. What is a Radar? and how it operates? 2. What are Radar types? and their advantages? 3. What information can we extract from the Radar? (mention 3) 4. Mention some Radar applications? Explain one of them? 5. Deﬁne the following terms: • Max unambiguous range? • Pulse-to-pulse, Scan-to-scan correlation?

etc. 2. Draw the block diagram of a standard Radar system? • Trace the received signal at each stage? • State the function of each part of the diagram: Duplexer. how can a target (ex: drone) cheat the radar?
2
. Is Basic radar equation pessimistic or optimistic. pulse integration. • Calculate the threshold voltage? (see example in the appendix) 4. etc ? 4. Matched Filter. . Illustrate eﬀect of pulse integration: • Calculate number of pulses that hit the target? • Coherent vs. 1.• Antenna gain. Non-coherent?
3
Analytical Questions
This section comes after the mathematical calculations. if compared with real world? Explain? 2. Illustrate the process of the threshold detection? • Mention two types of errors? • What eﬀect do the threshold have on them? plot to explain. Make a comment on your results. Based on what you have learned about Radar operation. Ampliﬁer gain (IF and RF stages). . Derive the radar equation? then • Express it in terms of SNR? • Add other factors to make it more accurate? • Remember you’ll need some curves when using Radar equation (ﬂuctuating targets. 3. ). What is the relationship between these factors: (try to repeat calculation on diﬀerent values and compare) • Rmax as function of PRF? • Rmax Peak power and pulse duration? • Rmax as function of operating frequency? • Rmax as function of target cross section? • Others . . 3. .

. Probability of detection (Pd )? 6. . and noise ﬁgure (F ). The receiver gain is (g ). Using your answers from parts (2) and (4) above. The target has a backscatter RCS of 2 m2 . 5. Find the noise power referred to the receiver input in watts and in dBW. The detection threshold is set 15 dB above the rms noise ﬂoor of the receiver. If the target is detected. rms noise voltage (σn )? assume resistor = rΩ 3. 3. then comment on the new results . A target is at a distance of 100 km from the radar. in W/m2 and in dBW/m2 . Change some parameters.4
Unsolved Examples
Example
Consider radar with transmitted power (Pt ). Determine the power ﬂux density at the target when the antenna points directly at it.
Example
A C-band surveillance radar has the following parameters: Frequency Receiver IF Bandwidth Pulse duration PRF Antenna Gain Transmit pulse power 5500 MHz 2. 2. The radar receiver has a system noise temperature of 800 K. Find the maximum received power at the input to the radar receiver in watts and dBW. bandwidth (B ) at room temperature. determine whether this target will be detected by the radar. Max range for ﬂuctuating target of type (X )? 7. Thermal noise ﬂoor (Pn )? 2.0 MHz 0. Voltage threshold required to achieve mean time between false alarm of (Tf a ) hours? 4. 4.5 microsecond 500 pps 40 dB 250 kW
1. and antenna gain (G). how many decibels is the signal above the threshold? 3
. Probability of false alarm (Pf a )? 5. Find the power level of the threshold in dBW. If the target was at range of (R) and have cross section of (σ dB) Find: 1. frequency (f ).

Use curves to estimate the non-coherent integration gain that can be achieved with this number of hits. Calculate the maximum range at which this radar can detect a 1m2 RCS target with a single pulse assuming a threshold set at 14 dB above rms noise. 8. The threshold setting of the radar is raised to 15. and no losses. Calculate the time between false alarms for this radar. 6. What is the new time between false alarms? 9.6.5 MW 38 dB 2. Calculate the 3 dB antenna beamwidth. what is the maximum range for the 5m2 target? 9.8 GHz 1. 7.0 dB. 2. 4
. What is the maximum range of the radar taking account of integration gain and losses? (Begin this calculation with your result from part (7)).0 ms 10 rpm 380 Hz 800 K 1. 4. The radar has losses that total 10. Calculate the number of hits on the target between the 3 dB points on the antenna pattern as the antenna beam scans the target. 5. What is the average RF power of the radar transmitter. What is the maximum unambiguous range for this radar? What is the smallest target RCS that can be detected at this range (i. 3. in dBW.e. If the threshold is lowered to 12 dB. Using the non-coherent gain you found in part (6) above ﬁnd the maximum range at which the radar can detect the 1m2 target with a 12 dB threshold. where received Power Pr = threshold level). Use this value in subsequent parts of this question. in km? 8.0 dB. Calculate the thermal noise power referred to the receiver input. 7. Calculate the maximum unambiguous range for the PRF of 380 Hz. in watts?
Example
A long range surveillance radar has the following speciﬁcation: Transmit pulse power Antenna gain RF frequency Transmitted pulse width Antenna rotation rate PRF Receive system noise temperature Receiver noise bandwidth 0. What is the maximum range at which a target with RCS = 5 m2 can be detected.0 MHz
1.

) 12. What is the disadvantage of the slower rotation rate?
5
. Is this true? If so. ﬁnd the new maximum range for the radar in clear air conditions (no rain in the path) and a PRF of 380 Hz.10. It is suggested that the performance of the radar could be improved by slowing the antenna rotation rate to 6 rpm. Dont forget that the radar signal must pass through the rain storm twice.8 GHz signals. the radar can be operated with a PRF of 650 Hz. Find the maximum range of the radar under these conditions. To resolve range ambiguity. (Use the base PRF of 380 Hz. A rainstorm is located at a distance of 50 km from the radar and causes 1 dB of attenuation to 2. What is maximum range when the 650 Hz PRF is used? 11.

so bring them with you.5
Radar Curves
Some of these curves might be needed in the exam. (Don’t write anything on them!)
6
.

7
.Figure 1: Probability of detection and function of SNR and Probability of false alarm.